Can he close the deal?

Clinton and Obama spent the final day of the campaign barnstorming across the primary states and hoping to turn out their respective bases and to win last minute converts to their campaigns. Voter in Texas, Ohio, Vermont and Rhode Island all go to the polls today.

The candidates also traded barbs on the campaign trail, with Clinton accusing Obama of duplicity on the North American Free Trade Agreement and Obama's camp pushing for Clinton to release her White House records as first lady. Clinton also rejected calls for her to drop out of the race, saying "I'm just getting warmed up."

The biggest prize of the day is Texas, which will decide on 228 delegates to the Democratic Convention this summer in Denver. All but 35 of those will be decided in the primary and caucuses today.  But Ohio is also important with 161 delegates at stake, 141 of which will be decided by the vote today. 

Obama holds a lead of more than 100 delegates (1392 to 1279), but neither candidate is close to reaching the 2,025 delegates needed to clinch the nomination. Even if Obama were to win all 370 delegates at stake today -- a virtual impossibility -- that would leave him 263 short of the nomination.

Sen. Clinton is facing mounting pressure to quit the Democratic race if she does not do well in Texas and Ohio today, but if she wins those states she will be able to argue that she has won every big state in the contest so far.  Clinton has already won California, New York, New Jersey and Massachusetts, and in nonbinding races in Florida and Michigan. Those are all key states a Democrat would like to win in the general election in November.